Why do I get error with this code?

import pandas as pd

# load the worldcities DataFrame

worldcities = pd.read_csv('worldcities.csv')

# group cities by country and count number of cities in each country

cities_per_country = worldcities.groupby('country')['city'].count().reset_index()

# rename columns to be more descriptive

cities_per_country.columns = ['Country', 'Number of Cities']

# sort countries by number of cities in descending order

cities_per_country = cities_per_country.sort_values(by='Number of Cities', ascending=False).reset_index(drop=True)

# create a list to store the top 10 countries by number of cities

top_10_countries = cities_per_country['Country'].head(10).tolist()

# create an empty DataFrame to store the final output

output_table = pd.DataFrame(columns=['Country', 'Number of Cities', 'Largest City', 'Population'])

# loop through top 10 countries and extract relevant data

for country in top_10_countries:

# filter cities in current country

cities_in_country = worldcities[worldcities['country'] == country]

# count number of cities in current country

num_cities = cities_in_country['city'].count()

# get city with highest population in current country

largest_city = cities_in_country.loc[cities_in_country['population'].idxmax(), 'city']

# get population of largest city in current country

population = cities_in_country.loc[cities_in_country['population'].idxmax(), 'population']

# add row to output_table DataFrame

output_table = output_table.append({'Country': country, 'Number of Cities': num_cities,

'Largest City': largest_city, 'Population': population},

ignore_index=True)

# print final output table

print(output_table)

This is the csv file, which has the heading country

This is the outcome: